Mailman 3 October 2002 - Cplusplus-sig

newbie questions
by Stefan Seefeld Oct. 8, 2002

Oct. 8, 2002

hi there, now that I have taken the first hurdles, I come back with more questions :) I want to create a python frontend for a set of libraries / modules I'm working with. I'v got an interface ('Foo') that is implemented at a couple of places ('FooImpl1', 'FooImpl2', etc.), and I have a factory that instantiates them depending on a string argument. It looks like the natural thing to do would be to make the python front end expose the interface 'Foo', but instead of exposing Foo's constructor, the Foo factory is used: > foo1 = Foo("FooImpl1") > foo2 = Foo("FooImpl2") How is this to be done ? It looks like I should play with 'HeldType', but I could't get it working yet. Also, If I use a 'class_' where the HeldType is a pointer type, how should I manage ownership ? Thanks a lot, Stefan

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Re: [C++-sig] Leaked reference when putting an
by Charsley, Mark Oct. 8, 2002

Oct. 8, 2002

> > I appear to be leaking a reference in my C++ extension. <SNIP> > > So is there something wrong with > > a) my code > > b) python's reference counting > > c) the boot.python library > Mark, it doesn't look like you're doing anything wrong, That's a shame: my code would have been the easiest to fix :-(. I'll switch to passing a python dictionary instead of my struct for the time being. > I can't fix the problem. The Boost Python v1 codebase is going to be > retired this week; we're releasing v2, Oh well I'll keep an eye out at boost.org each for the new release. TVM Mark ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify postmaster(a)radioscape.com. This footnote also confirms that this email message has been scanned for the presence of computer viruses known at the time of sending. www.radioscape.com **********************************************************************

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Leaked reference when putting an extension object in a tuple
by Charsley, Mark Oct. 7, 2002

Oct. 7, 2002

I appear to be leaking a reference in my C++ extension. The general gist of what I'm trying to achieve is to create a C++ python extension that a) defines a new class (MyClass) b) provides a way for python to register callback functions When a callback becomes necessary, my extension creates a MyClass object, puts it in a tuple and then calls PyEval_CallObject with the callback function and the tuple. Unfortunately it seems to leak references when I put my object in a tuple. The source for a very cut down version of the extension is given below. Running it in a debug build of python gives the following... ActivePython 2.2.1 Build 222 (ActiveState Corp.) based on Python 2.2.1 (#34, Apr 10 2002, 11:35:50) [MSC 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import PyObjectPasser [8031 refs] >>> PyObjectPasser.RequestCallback() [8034 refs] >>> PyObjectPasser.RequestCallback() [8035 refs] >>> PyObjectPasser.RequestCallback() [8036 refs] >>> PyObjectPasser.RequestCallback() [8037 refs] >>> Putting an integer into the tuple instead of a MyClass object gives a constant count of 8033 refs. So is there something wrong with a) my code b) python's reference counting c) the boot.python library In the probable case of a), what am I doing wrong? Many thanks in advance Mark code follows... 8<------------------------------------------------------------------- #include <boost/python/class_builder.hpp> #include <boost/python/objects.hpp> struct MyClass { MyClass() { m_priority = 0; } MyClass(int priority) { m_priority; } int m_priority; }; void RequestCallback(); namespace { BOOST_PYTHON_MODULE_INIT(PyObjectPasser) { boost::python::module_builder this_module("PyObjectPasser"); boost::python::class_builder<MyClass> MyClassBuilder(this_module, "MessageInfo"); MyClassBuilder.def(boost::python::constructor<>()); MyClassBuilder.def(boost::python::constructor<int>()); MyClassBuilder.def_readonly(&MyClass::m_priority, "priority"); this_module.def(RequestCallback,"RequestCallback"); } } void RequestCallback() { // create an object of our class MyClass obj(1); // we call a python function in the real code, so build up a tuple // of arguments boost::python::tuple args(1); // put our object in the tuple args.set_item(0,obj); // would now call the callback here } 8<------------------------------------------------------------------- ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify postmaster(a)radioscape.com. This footnote also confirms that this email message has been scanned for the presence of computer viruses known at the time of sending. www.radioscape.com **********************************************************************

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compiling boost.python v2 on IRIX
by Stefan Seefeld Oct. 7, 2002

Oct. 7, 2002

hi there, I just tried to compile boost.python v2 on irix using the 'mipspro' toolset. The compilation failed on the file 'pickle_support.o' with the error(s) cc-3354 CC: ERROR File = /homes/Developer/sseefel/boost/boost/mpl/aux_/preprocessed/plain/arg.hpp, Line = 18 A non-integral operation is not allowed in a nontype template argument. BOOST_STATIC_ASSERT(!is_void_<type>::value); ^ cc-1070 CC: ERROR File = /homes/Developer/sseefel/boost/boost/mpl/aux_/preprocessed/plain/arg.hpp, Line = 18 The indicated type is incomplete. BOOST_STATIC_ASSERT(!is_void_<type>::value); Beside that, I find the build system not very transparent, so tracking things down is non-obvious. The use of jam isn't particularly helpful. For example I just realized from the error logs that it is using the "-mips3" compiler flag, while I'd like "-mips4". I couldn't find either docs nor code that made clear how to change that flag. Any help would be highly appreciated ! Regards, Stefan

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mac os x
by Ralf W. Grosse-Kunstleve Oct. 7, 2002

Oct. 7, 2002

I am trying to install the latest Boost.Python code on a freshly installed Mac OS 10.2 with the Jun or Jul developer's kit + Aug patch. With a very minor fix compilation of the core library goes smoothly, but my first attempt at linking libbpl.dylib failed miserably. See attached log. I'd be grateful if any of the Apple experts out there could help figuring out what is wrong. Ralf c++ -fno-common -no-cpp-precomp -ftemplate-depth-50 -w -g -DNDEBUG -DBOOST_PYTHON_DYNAMIC_LIB -DBOOST_PYTHON_V2 -DBOOST_PYTHON_SOURCE -I/net/cci/rwgk/mpl2/boost -I/usr/include/python2.2 -c -o boost/libs/python/src/tuple.o /net/cci/rwgk/mpl2/boost/libs/python/src/tuple.cpp c++ -dynamiclib -o libtbx/libbpl.dylib boost/libs/python/src/list.o boost/libs/python/src/long.o boost/libs/python/src/dict.o boost/libs/python/src/tuple.o boost/libs/python/src/str.o boost/libs/python/src/aix_init_module.o boost/libs/python/src/converter/from_python.o boost/libs/python/src/converter/registry.o boost/libs/python/src/converter/type_id.o boost/libs/python/src/object/enum.o boost/libs/python/src/object/class.o boost/libs/python/src/object/function.o boost/libs/python/src/object/inheritance.o boost/libs/python/src/object/life_support.o boost/libs/python/src/object/pickle_support.o boost/libs/python/src/errors.o boost/libs/python/src/module.o boost/libs/python/src/converter/builtin_converters.o boost/libs/python/src/converter/arg_to_python_base.o boost/libs/python/src/object/iterator.o boost/libs/python/src/object_protocol.o boost/libs/python/src/object_operators.o ld: multiple definitions of symbol _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same boost/libs/python/src/list.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/dict.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/str.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/converter/from_python.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) ld: multiple definitions of symbol _ZZN5boost6python6detail11upcast_implI11_typeobject7_objectEEPT0_PT_S6_E4same boost/libs/python/src/converter/from_python.o definition of _ZZN5boost6python6detail11upcast_implI11_typeobject7_objectEEPT0_PT_S6_E4same in section (__TEXT,__const) boost/libs/python/src/object/enum.o definition of _ZZN5boost6python6detail11upcast_implI11_typeobject7_objectEEPT0_PT_S6_E4same in section (__TEXT,__const) boost/libs/python/src/object/enum.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object/class.o definition of _ZZN5boost6python6detail11upcast_implI11_typeobject7_objectEEPT0_PT_S6_E4same in section (__TEXT,__const) ld: multiple definitions of symbol _ZZN5boost6python6detail11upcast_implI11_typeobjectS3_EEPT0_PT_S5_E4same boost/libs/python/src/object/enum.o definition of _ZZN5boost6python6detail11upcast_implI11_typeobjectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object/class.o definition of _ZZN5boost6python6detail11upcast_implI11_typeobjectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object/class.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object/function.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object/life_support.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object/pickle_support.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/module.o definition of _ZZN5boost6python6detail11upcast_implI11_typeobject7_objectEEPT0_PT_S6_E4same in section (__TEXT,__const) boost/libs/python/src/module.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/converter/builtin_converters.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/converter/arg_to_python_base.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object_protocol.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) boost/libs/python/src/object_operators.o definition of _ZZN5boost6python6detail11upcast_implI7_objectS3_EEPT0_PT_S5_E4same in section (__TEXT,__const) /usr/bin/libtool: internal link edit command failed __________________________________________________ Do you Yahoo!? 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deepcopy
by Ralf W. Grosse-Kunstleve Oct. 7, 2002

Oct. 7, 2002

Sometimes I need to make a copy of a wrapped C++ object in Python. Python's copy.deepcopy() will only work for objects that are pickleable. I am wondering if it wouldn't be easy to make the C++ copy constructor available by default in Python, for example through the member functon .copy(). That would be much more convenient than .def'ing copy for everything explicitly. Similar to "no_init" there could be a "no_copy" to suppress the automatic generation of .copy(). Ralf __________________________________________________ Do you Yahoo!? Faith Hill - Exclusive Performances, Videos & More http://faith.yahoo.com

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Pointer manipulation Boost.Python - C++
by Mathieu Tremblay Oct. 5, 2002

Oct. 5, 2002

Hello, I am taking a look at Boost.Python and I wonder if it is possible to convert pointers to existing classes to PyObjects* and then be able to pass an existing instance of an object directly to and from python: Example: In C++ I create a CWheel and I set its member m_diameter to 1233. In python I have a function that receives a CWheel and displays the diameter (Lets suppose that Python knows the CWheel from Boost.Python :-) ) Ex : def printCWheelDiam(awheel): print awheel.m_diameter What I would like to do Is to create the CWheel in C++, pass its pointer to python so it can manipulate it (and see that its diameter is 1233) and then return a CWheel that I could map from a PyObject to a CWheel in C++. In SWIG, it was easy to convert the pointers with the function : C++ to Python : MYSWIG_NewPointerObj Python to C++: MYSWIG_ConvertPtr Do you have an equivalent to these functions ? Or can you point me to documentation that explains how to do it ? Thanks again, Mathieu Tremblay mtremblay(a)golemlabs.com

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Boost.Python v2: MinGW-2.0 support
by David Abrahams Oct. 4, 2002

Oct. 4, 2002

I have just checked in the changes to the main trunk neccessary to support MinGW-2.0. All tests are passing. Enjoy, Dave ----------------------------------------------------------- David Abrahams * Boost Consulting dave(a)boost-consulting.com * http://www.boost-consulting.com

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Trunk OK?
by David Abrahams Oct. 4, 2002

Oct. 4, 2002

According to my tests, things on the CVS main trunk are working again for Boost.Python v2. ----------------------------------------------------------- David Abrahams * Boost Consulting dave(a)boost-consulting.com * http://www.boost-consulting.com

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Boost.Python v2: A few small changes
by David Abrahams Oct. 3, 2002

Oct. 3, 2002

In preparation for release, I've been working on documentation. When I read my documentation, I sometimes get an uncomfortable feeling about what I have to write and realize it would be better to fix the implementation. A few small changes are happening now as a result: 1. The BOOST_PYTHON_[MEMBER_]FUNCTION_OVERLOADS macros used to expose functions with default arguments will not be available by simply #including <boost/python/class.hpp> or <boost/python/def.hpp>. Instead they will be moved to <boost/python/overloads.hpp> 2. The module class is officially disappearing, for real. I'm going to keep module.hpp, but only so I can do: #include <boost/python/module_init.hpp> #define BOOST_PYTHON_MODULE BOOST_PYTHON_MODULE_INIT BOOST_PYTHON_MODULE_INIT will continue to be available but deprecated for Boost 1.29.0, but the "official" macro will be BOOST_PYTHON_MODULE By the way, I've been pondering the merits of having a <boost/python.hpp> header which exposes all of the public headers, just for ease-of-use. Opinions? ----------------------------------------------------------- David Abrahams * Boost Consulting dave(a)boost-consulting.com * http://www.boost-consulting.com

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